In telecommunications, a femtocell—originally known as an Access Point Base Station—is a small base station, typically designed for use in a home or small business. The femtocell incorporates the functionality of a typical base station but extends it to allow a simpler, self-contained deployment.
For a mobile operator or a service provider, the attractions of a femtocell are improvements to both coverage and capacity, especially indoors. Femtocells can provide opportunity for new services and reduced cost. The mobile operator not only benefits from the improved capacity and coverage but also can reduce both capital expenditure and operating expense.
A typical situation includes system base stations being located outside, and the femtocells being located indoors. The system base stations are typically synchronized to a network (such as, global positioning system (GPS) signals), wherein the system base station can include any one of a macro, micro or pico base station that is synchronized to GPS. Because the base stations are synchronized, the base stations are able to synchronize their communications, and therefore, minimize the overall interference between themselves and any mobile unit connected to the base stations. However, femtocells are frequently located indoor and cannot receive global positioning system (GPS) signals, and therefore, are not tightly synchronized to the rest of the network.
Femtocells are typically simplified and low power base stations. The femtocells typically have lower coverage than system base stations and are IP-backhaul connected through a local broadband connection such as DSL, cable, PON or a fixed wireless backhaul. As mentioned, being located indoors, femtocells generally cannot receive GPS signals. Therefore, a femtocell in a time division duplex (TDD) systems (such as WiMAX) lack precise timing synchronization and can cause interference between wireless transmissions of femtocell and base stations.
It is desirable to have a method and apparatus for improving synchronization of femtocells to base stations of a network, and to reduce interference in the network.